rmt-tar

is a program used by tar, cpio, mt, and the remote dump and restore programs in manipulating a magnetic tape drive through an interprocess communication connection. is normally started up with an rexec(3) or rcmd(3) call or the rsh(1) command.

The program accepts requests specific to the manipulation of magnetic tapes, performs the commands, then responds with a status indication. All responses are in and in one of two forms. Successful commands have responses of:

is an representation of a decimal number. Unsuccessful commands are responded to with:

is one of the possible error numbers described in intro(2) and is the corresponding error string as printed from a call to perror(3) The protocol is comprised of the following commands, which are sent as indicated - no spaces are supplied between the command and its arguments, or between its arguments, and indicates that a newline should be supplied:

• device Open the specified using the indicated is a full pathname and is an representation of a decimal number suitable for passing to open(2) If a device had already been opened, it is closed before a new open is performed.
• \n Close the currently open device. The specified is ignored.
• L Perform an lseek(2) operation using the specified parameters. The response value is that returned from the call.
• \n Write data onto the open device. reads bytes from the connection, aborting if a premature end-of-file is encountered. The response value is that returned from the write(2) call.
• \n Read bytes of data from the open device. If exceeds the size of the data buffer (10 kilobytes), it is truncated to the data buffer size. then performs the requested read(2) and responds with if the read was successful; otherwise an error in the standard format is returned. If the read was successful, the data read is then sent.
• operation Perform a ioctl(2) command using the specified parameters. The parameters are interpreted as the representations of the decimal values to place in the and fields of the structure used in the call. The return value is the parameter when the operation is successful.
• S Return the status of the open device, as obtained with a call. If the operation was successful, an ``ack'' is sent with the size of the status buffer, then the status buffer is sent (in binary).

Any other command causes to exit.

All responses are of the form described above.

tar(1) cpio(1) mt(1) rsh(1) rcmd(3) rexec(3) mtio(4) rdump(8) rrestore(8)

People should be discouraged from using this for a remote file access protocol.

The command appeared in x 4.2 .